| Objective:Relapse refers to a behavior of taking addictive drug again after abstinence. It is an important character in drug addiction. As we know, there are three stimulating factors to induce relapse: (1) environmental stimulus related to previously drug-taking;(2) in sight of drug itself;(3) stressful event. Environmental stimulus related to previously drug-taking is the chief one in three factors. In animal experiment for the relapse research, environmental stimulus can establish relation with drug through conditioned reflection and gain the ability for triggering behaviour of the relapse, which can induce conditioned place preference. The mesolimbic dopaminergic system (MLDS) is a crucial part to induce psychological dependence by opiate drug and is the neurophysiological base of drug addiction, cytons of Mesolimbic dopaminergic neurone mostly locate in ventral tegmental area (VTA) and throw nerve fiber at nucleus accumbence (NAc). It is universally acknowledged that NAc is the key to psychological dependence of drug. NAc of addictive rat is motivated by electrical stimulation in this experiment to investigate the effect on the building of psychological dependence of rat. Methods:1.Implant of outer thimble of coaxial stainless electrode in bilateral NAc of rat: Rat is fastened to stereotaxic instrument after anaesthetic. 2.Establishment of rat model of psychological dependence: 30 rats after electrode implantation are divided into 3 teams with ten each group:morphine-stimulation team, morphine-fake stimulation team and saline team, there is one injection in the morning and afternoon respectively with morphine while the other with saline for rats in the first and second team. The third team is trained with saline as control. 3.Electrical stimulation of NAc of rat: morphine-stimulation team under anaesthetic are fastened after train everyday, then two poles of coaxial stainless electrode are connected to JL-C2 electrical stimulator, morphine-stimulation team is stimulated and morphine-fake stimulation team is not stimulated. 4.Comparing CPP scores of three groups in test stage: after train stage(6 days), CPP scores are compared in every stage. Result:l.The average time in black case of saline control group is not obviously different comparing pre-train with post-train in the 10 days after training. 2. The average time in white case of morphine-fake stimulation team is longer in 1st day of post-train than the one of pre-train (P >0.01),but the difference is not obvious. From 2rd day , The average time in white case of morphine-fake stimulation team is longer than the one of pretrain (P <0.01).It indicates that rats of morphine-fake stimulation team show obvious preference to white case.The average time in white case of morphine-fake stimulation team is longer than the time of saline control team from 2st day after training.lt is remarkablely different ( P <0.01) .It suggests that the model of morphine-induced psychological preference is builded up. 3.From 1st day after training, the average time of rats of morphine-stimulation team staying in the white case is longer than the one of pre-training( /><0.01 ).It indicates that rats of morphine-stimulation team show preference to white case. 4.After training under conditions of stimulation, the average time of rats of morphine-stimulation team staying in the white case is longer than the one of morphine-fake stimulation team( P <0.01) .It indicates that formation of behaviors of CPP are promoted remarkablely in rats. It suggested that morphine-induced psychological dependence of rats can be strengthed under electrical stimulation. Conclusion:1. It is the method used in the experiment that can build up a rat model of morphine-induced psychological dependence in a short time.2. It is motivating NAc of rats by 80Hz, 0.2ms, 5V electrical stimulation that can obviously promote formation of morphine-induced CPP behaviors.lt testifies that morphine-induced psychological dependence is strengthened by 80Hz electrical stimulation. |
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